Vegas Golden Knights left wing Erik Haula knocks the puck away from goaltender Marc-Andre Fleury during the second period of an NHL hockey game against the Colorado Avalanche, Monday, March 26, 2018, in Las Vegas. (AP Photo/John Locher)AP | AP

Vegas Golden Knights left wing Erik Haula knocks the puck away from goaltender Marc-Andre Fleury during the second period of an NHL hockey game against the Colorado Avalanche, Monday, March 26, 2018, in Las Vegas. (AP Photo/John Locher)AP | AP

LAS VEGAS — William Karlsson and Jonathan Marchessault each scored to help the expansion Vegas Golden Knights clinch a playoff spot with a 4-1 win over the Colorado Avalanche on Monday night.

The Golden Knights became the first team to reach the playoffs in its inaugural season since the league expanded for the 1967-68 season.

It was also the 200th career victory for coach Gerard Gallant.

Alex Tuch and Shea Theodore also scored for Vegas, and Marc-Andre Fleury improved to 28-11-4 after stopping 28 shots.

The Golden Knights host San Jose on Saturday and are six points in front of the Sharks in the Pacific Division. San Jose beat Chicago in overtime earlier Monday.

Erik Johnson scored for the Avalanche and Semyon Varlamov made 26 saves.

The Avalanche are fourth in the Central Division but hold the top wild card in the Western Conference, just in front of St. Louis.

Tuch was in the right spot on Vegas’ first power play to punch home a loose puck and give the Golden Knights a 1-0 lead.

Colorado tied it when Johnson was there to fire in a rebound.

Vegas went back up 2-1 when Marchessault beat Varlamov with a slick wrist shot. Vegas has scored with a man advantage in 20 of its last 31 games.

The Golden Knights wasted no time in extending their lead in the third period, when Erik Haula fed a streaking Theodore, who put one past Varlamov at the 1:31 mark.

Karlsson closed out the scoring with an empty-net goal, his 40th of the season.

Colorado is 11-7-3 against the Pacific Division and dropped to 7-3-3 in March. The Avalanche are still riding a 9-3-3 streak but had a three-game road winning streak snapped.

NOTES: The Avalanche had three players skate in milestone games, as Landeskog played in his 500th game, Tyson Barrie played in his 400th, and Gabriel Bourque notched his 300th. … Vegas’ James Neal is now three games shy of his 700th. … Marchessault became the 10th player in NHL history to record 70+ points while playing for a team in its inaugural season. … The 18,326 in attendance was the third-largest crowd of the season.